1. Field of the Invention
The subject matter of the present invention is a method wheeby chlorosilanes can be obtained simultaneously with aromatic aldehydes or caroboxylic acid chlorides or ethers, without substantial production of by-products.
2. Discussion of Prior Art
Chlorosilanes, carboxylic acid chlorides and aromatic aldehydes are known intermediates used in many technical syntheses for the production of silylation products or protective-group reagents, as well as dyes, pharmaceutical products and scents.
Chlorosilanes are produced in technical amounts in the process known as "Rochow synthesis." One disadvantage of this process is the inhomogenity of the products, which necessitates fractional distillation, resulting in a large amount of useless by-products.
Aromatic aldehydes and carboxylic acid chlorides are prepared technically by the reaction of chloromethylbenzenes with water or aromatic carboxylic acids in the presence of catalysts, with the splitting off of hydrogen chloride. In these processes the performance of the hydrolysis presents technical difficulties, or it is necessary to use as starting products the carboxylic acids prepared by separate steps of the process, thereby making the overall process very expensive. All of the processes additionally have the great disadvantage that the hydrogen chloride formed in the reaction has to be removed from the reaction vessel and then subjected to an absorption and/or purification. Furthermore, the hydrogen chloride in many of the above-named reaction products, such as 3-chlorophthalide, for example, results in a loss of storage life. It must, therefore be completely removed from the reaction product. This additional procedure often requires a great deal of work.
Furthermore, many of the applications of the siloxanes or silicones or of the trialkylsilyl compounds suffer from the fact that in them by-products are produced for which there are not many uses. Such unusable by-products are formed in the synthesis of antibiotics, for example (e.g., cephalosporin derivatives) on account of the protection of sensitive groupings by silyl groups in the form of hexamethylsiloxanes, or they are formed in the use of siloxanes as hydraulic oils or heat transfer agents in the form of used or contaminated oil. Often these by-products have to be destroyed, because working them up by the known cleavage of siloxanes with hydrogen chloride in the presence of sulfuric acid or aluminum chloride requires a great deal of trouble and is not optimal.
The problem therefore existed of utilizing the by-products and of recycling them into the process insofar as possible. Furthermore, it has been a long-standing problem to improve the technical preparation of alkyl chlorosilanes and to make them independent of the Rochow synthesis and its disadvantages. The third problem to be solved was the development of a process for the preparation of aromatic carbonyl compounds from chlorinated methylbenzenes, in which the hydrogen chloride that is produced is directly utilized.